How do I do enemy respawn?

i am trying to make a enemy respawning system like in the classic Megaman games without enemy spawners. when an enemy exits the screen it won't respawn until its spawn point is not screen (the spawn point is the x and y coordinates where it was created and the coordinates where the enemy will respawn).

my problem is that i can't find a way to prevent it to respawn on screen

this was my attempt

dropbox.com/s/fhdm9131ssehb7v/enemy%20respawn%20test.c3p

i am just asking if you have a way to prevent it to respawn on the screen please. and sorry if my English is not that good